I just got a 89 supra turbo and replaced the factory turbo, but the car lacks a little power. It needs a bit of a tune up. believe me, but I think most of the power loss is from a small exhaust leak near the downpipe/manifold area. I bolted those gaskets down like a mother f***** so I think the leak is coming from elsewhere like a faulty, rusted out weld near the cat or something. If you can help me out, that would be sweet!!! k thanks!!
The exhaust leak will cause a boost loss in the system. But over-tigntening gaskets can be just as harmful if they deform and leave an open leak area between the two sealing points.
Get your exhaust leak fixed, and purchase a new set of gaskets. Then follow the manufacturer's Torque Specs for the proper tightening procedures.
If you over tighten them there is a possibility your can also warp the mounting surfaces for the gaskets and or the Turbo Charger. Then you are going to be into a real bill for parts and labor. Especially if you damage the Turbo Charger. Those baby's are about $1200.00 bucks re-built, and close to $2000.00 new.
Toyota does not build their Turbo Chargers, they subcontract to Garrett. Those are big dollar turbos.
You might want to consider that before getting the pipe extension for your wrench! 
He He He!
After the turbo-charger can be an issue to, as some of the waste gate systems have a pressure monitor tube that will open the gate at a specific amount of exhaust pressure.
But I don't know if your car is equipped with such a device. It could be computer controlled, and if it is there is a sensor inthe system that monitors Intake Pressure, this may be a MAP Sensor Issue too.
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